1. Field of the Invention
The present invention relates to a camera shutter unit adapted to a digital still camera or the like and, more particularly to a camera shutter unit which is separately provided with a shutter blade for opening and closing an exposure aperture and a diaphragm blade for stopping down the aperture.
2. Description of the Related Art
Unexamined Japanese Patent Publication kokai) No.10-221740, for example, discloses a conventional camera shutter unit which is separately provided with a shutter blade for opening and closing an exposure aperture where through light passes and a diaphragm blade for stopping down the aperture.
This camera shutter unit includes a shutter blade arranged at a periphery of the aperture so as to move back and forth to open and close the aperture, one electromagnetic drive source for driving the shutter blade, a diaphragm blade arranged so as to move back and forth to stop down the aperture and release the stopping-down, and another electromagnetic drive source for driving the diaphragm blade.
Thereupon, when respective electromagnetic drive sources start, the shutter blade moves back and forth between an opening position wherein the aperture is opened and a closing position wherein the aperture is closed to open and close the aperture and the diaphragm blade moves back and forth between a stopping-down position wherein the aperture is stopped down and an evacuating position wherein the aperture is not stopped down. Also, when respective electromagnetic drive sources are not energized, the shutter blade is held in either the opening position or the closing position and the diaphragm blade is held in either the stopping-down position or the evacuating position.
By the way, with respect to the above conventional camera shutter unit, separate drive sources are provided for driving the shutter blade and the diaphragm blade. Therefore, the shutter blade and the diaphragm blade can be driven separately without using a complicated linkage. However, since separate electromagnetic drive sources are provided, the unit is large-sized, heavyweight, high-cost or the like and consumes a large amount of power in accordance with the number of electromagnetic drive sources.
Also, upon drive of the diaphragm blade and so on, in case only the electromagnetic drive source starts to move the diaphragm blade, when being positioned in a predetermined stopping-down position, the diaphragm blade may bounce and therefore, when stopping down rapidly, the response characteristic of diaphragm blade is not preferable.
In view of the foregoing, an object of the present invention is to provide a a camera shutter unit which adopts a mechanism for interlocking a diaphragm blade with a shutter blade without complexity of the unit so that the shutter blade and the diaphragm blade can function reliably and the diaphragm blade can be positioned to perform a desired stopping-down operation reliably, with a small size, lightweight, low-cost, or the like.
To achieve the above-mentioned object, a camera shutter unit according to the first aspect of the present invention comprises a base plate having an exposure aperture, a diaphragm blade arranged to be capable of moving between a stopping-down position wherein the aperture is stopped down and an evacuating position wherein the aperture is opened (is not stopped down), a shutter blade arranged to be capable of moving between an opening position wherein the aperture is opened and a closing position wherein the aperture is dosed, and a drive-control mechanism for drive-controlling the shutter and diaphragm blades. The drive-control mechanism is composed of a single electromagnetic drive source which can drive the shutter and diaphragm blades to interlock the diaphragm blade with the shutter blade such that the opening position corresponds to the evacuating position and a travel of from a way position between the opening position and the dosing position to the closing position corresponds to the stopping-down position, a restricting means for restricting movement of the shutter blade toward the dosing position when the diaphragm blade is positioned in the stopping-down position and for releasing its restriction by a predetermined or more level drive force which is generated by the electromagnetic drive source, and a control means for controlling the electromagnetic drive source. The control means controls, when moving to position the diaphragm blade in the stopping-down position, to move the shutter blade to the closing position in advance and next move in reverse the shutter blade by a predetermined amount.
Accordingly, when the single electromagnetic drive source starts, the shutter blade moves from the opening position to the closing position or from the closing position to the opening position, and the diaphragm blade moves from the evacuating position to the stopping-down position or from the stopping-down position to the evacuating position while following the shutter blade. Thus, the single electromagnetic drive source can drive the shutter and diaphragm blades and there is provided the restricting means, which can restrict movement of the shutter blade and can release its restriction, in accordance with the amount of drive force generated by the electromagnetic drive source. Therefore, the shutter and diaphragm blades can function reliably and the unit can be downsized, lightened, or the like. Also, in case the stopping-down operation by the diaphragm blade is carried out, the diaphragm blade is first moved to the dosing position and then is moved in reverse by a predetermined amount, thereby being positioned in the stopping-down position. Therefore, the bouncing of diaphragm blade upon stopping-down operation can be restrained or prevented, whereby the stopping-down operation can be carried out rapidly and reliably.
A camera shutter unit according to the second aspect of the present invention comprises a base plate having an exposure aperture, a diaphragm blade arranged to be capable of moving between a stopping-down position wherein the aperture is stopped down and an evacuating position wherein the aperture is opened (is not stopped down), a shutter blade arranged to be capable of moving between an opening position wherein the aperture is opened and a closing position wherein the aperture is closed, and a drive-control mechanism for drive-controlling the shutter and diaphragm blades. The drive-control mechanism is composed of a single electromagnetic drive source which can drive the shutter and diaphragm blades to interlock the diaphragm blade with the shutter blade such that the opening position corresponds to the evacuating position and a travel of from a way position between the opening position and the closing position to the closing position corresponds to the stopping-down position, a restricting means for restricting movement of the shutter blade toward the dosing position when the diaphragm blade is positioned in the stopping-down position and for releasing its restriction by a predetermined or more level drive force which is generated by the electromagnetic drive source, and a control means for controlling the electromagnetic drive source. The control means controls, when moving to position the diaphragm blade in the stopping-down position, to move the shutter blade up to a nearby position beyond a way position corresponding to the stopping-down position in advance and next move in reverse the shutter blade by a predetermined amount.
Accordingly, when the single electromagnetic drive source starts, the shutter blade moves from the opening position to the closing position or from the closing position to the opening position, and the diaphragm blade moves from the evacuating position to the stopping-down position or from the stopping-down position to the evacuating position while following the shutter blade. Thus, the single electromagnetic drive source can drive the shutter and diaphragm blades and there is provided the restricting means, which can restrict movement of the shutter blade and can release its restriction, in accordance with the amount of drive force generated by the electromagnetic drive source. Therefore, the shutter and diaphragm blades can function reliably and the unit can be downsized, lightened, or the like. Also, in case the stopping-down operation by the diaphragm blade is carried out, the diaphragm blade is fast moved up to a nearby position beyond a way position corresponding to the stopping-down position and then is moved in reverse by a predetermined amount, thereby being positioned in the stopping-down position. Therefore, the bouncing of diaphragm blade upon stopping-down operation can be restrained or prevented, whereby the stopping-down operation can be carried out rapidly and reliably.
In the above units according to the first and second aspects, when moving to position the diaphragm blade in the stopping-down position, the control means may control the electromagnetic drive source so as to decrease electric current continuously, so as to decrease electric current in the form of steps, or so as to decrease electric power continuously. Accordingly, the stopping-down operation can be carried out rapidly and reliably, and the response characteristic of diaphragm blade can be improved.
A camera shutter unit according to the third aspect of the present invention comprises a base plate having an exposure aperture, a diaphragm blade arranged to be capable of moving between a stopping-down position wherein the aperture is stopped down and an evacuating position wherein the aperture is opened (is not stopped down), a shutter blade arranged to be capable of moving between an opening position wherein the aperture is opened and a closing position wherein the aperture is closed, and a drive-control mechanism for drive-controlling the shutter and diaphragm blades. The drive-control mechanism is composed of a single electromagnetic drive source which can drive the shutter and diaphragm blades to interlock the diaphragm blade with the shutter blade such that the opening position corresponds to the evacuating position and a travel of from a way position between the opening position and the closing position to the closing position corresponds to the stopping-down position, a restricting means for restricting movement of the shutter blade toward the closing position when the diaphragm blade is positioned in the stopping-down position and for releasing its restriction by a predetermined or more level drive force which is generated by the electromagnetic drive source, and a control means for controlling the electromagnetic drive source. The control means controls, when moving to position the diaphragm blade in the stopping-down position, to move the diaphragm blade from the evacuating position to the stopping-down position gradually.
Accordingly, when the single electromagnetic drive source starts, the shutter blade moves from the opening position to the closing position or from the closing position to the opening position, and the diaphragm blade moves from the evacuating position to the stopping-down position or from the stopping-down position to the evacuating position while following the shutter blade. Thus, the single electromagnetic drive source can drive the shutter and diaphragm blades and there is provided the restricting means, which can restrict movement of the shutter blade and can release its restriction, in accordance with the amount of drive force generated by the electromagnetic drive source. Therefore, the shutter and diaphragm blades can function reliably and the unit can be downsized, lightened, or the like. Also, in case the stopping-down operation of the diaphragm blade is carried out, the diaphragm blade is gradually moved from the evacuating position to the stopping-down position, thereby being positioned in the stopping-down position. Therefore, the bouncing of diaphragm blade upon stopping-down operation can be restrained or prevented, whereby the stopping-down operation can be carried out rapidly and reliably.
In the above unit according to the third aspect, when moving to position the diaphragm blade in the stopping-down position, the control means may control the electromagnetic drive source so as to increase electric current continuously, so as to increase electric current in the form of steps, or so as to increase electric power continuously. Accordingly, the stopping-down operation can be carried out rapidly and reliably, and the response characteristic of diaphragm blade can be improved.
Also, in the above units according to the first to third aspects, after positioning the shutter blade in the closing position, the control means may control the electromagnetic drive source so as to decrease electric current to a predetermined level that can hold the shutter blade in the closing position or so as to decrease electric power to a predetermined level that can hold the shutter blade in the closing position. Accordingly, the power consumption of the unit can be reduced and damage to the electromagnetic drive source caused by exothermic reaction can be prevented.
Also, in the above units according to the first to third aspects, in accordance with each operation of the shutter blade and the diaphragm blade, the control means may control the electromagnetic drive source so as to change electric current or so as to change electric power. Accordingly, efficient control suitable for each operation can be performed, whereby the power consumption of the unit can be reduced and the stopping-down operation can be carried out reliably and further the response characteristic of diaphragm blade can be improved.
In the above units, the units may comprise a torsion spring for interlocking the diaphragm blade with the shutter blade, and one end of the torsion spring is hooked on the diaphragm blade and another end of the torsion spring is hooked on the shutter blade. Accordingly, the looseness between the shutter and diaphragm blades can be absorbed, whereby the variation in initial setting load of the torsion spring can be restricted or prevented.
In the above units, the units may comprise a spring engaged with a part of the electromagnetic drive source in order to position and hold the shutter blade in the opening position and the diaphragm blade in the evacuating position, with the electromagnetic drive source being non-energized. Accordingly, since the spring holds the shutter blade in the opening position and the diaphragm blade in the evacuating position, in comparison with the case using a magnetic attracting force, the variation in holding force can be reduced, and the number of composing parts can be reduced.
In the above units, the units may comprise a spring engaged with a part of the electromagnetic drive source in order to position and hold the shutter blade in the way position and the diaphragm blade in the stopping-down position, with the electromagnetic drive source being non-energized. Accordingly, since the spring holds the shutter blade in the way position and the diaphragm blade in the stopping-down position, in comparison with the case using a magnetic attracting force, the variation in holding force can be reduced, and the number of composing parts can be reduced.
In the above units, the restricting means may be of a torsion spring which urges the shutter blade toward the opening position when the shutter blade is located between the closing position and the way position wherein the diaphragm blade is in the stopping-down position, and which has a straight contact portion capable of coming in contact with the shutter blade and inclined to a plane wherein the shutter blade moves. Accordingly, a working force between the torsion spring serving as a restricting means and the shutter blade, namely, a force of the shutter blade that deforms the torsion spring or a force of the torsion spring that pushes the shutter blade is efficiently and reliably transmitted.
In the above unit, an arm portion of the torsion spring supporting the straight contact portion may extend perpendicular to a moving direction of the shutter blade. Accordingly, the operation loss of the torsion spring can be reduced and its urging force can act on the shutter blade efficiently. This allows the shutter blade and the torsion spring to work stabely.
In the above units, the electromagnetic drive source may be composed of a rotor having a driving pin, a coil for energizing, and a yoke forming a magnetic circuit. The diaphragm blade may have a first contact portion with which the driving pin comes in contact temporarily to drive enroute to the stopping-down position from the evacuating position. Accordingly, in addition that the diaphragm blade moves while following the shutter blade, since the driving pin comes in contact with the first contact portion temporarily to drive the diaphragm blade directly namely to kick the diaphragm blade, the response characteristic of diaphragm blade can be improved.
In the above units, the electromagnetic drive source may be composed of a rotor having a driving pin, a coil for energizing, and a yoke forming a magnetic circuit. The diaphragm blade may have a second contact portion which extends perpendicular to a moving direction of the driving pin in both side regions of the stopping-down position and the evacuating position and with which the driving pin comes in contact to drive. Accordingly, since there is provided the second contact portion, which extends perpendicular to the moving direction of the driving pin in both side regions of the stopping-down position and the evacuating position, namely, which has edge portions extending toward the rotation center of the rotor in both nearby regions close to the stopping-down position and the evacuating position, the operating angle of the diaphragm blade can be increased without enlarging the range of rotation angle of the rotor. Consequently, in case the rotation angle of the rotor is limited, the unit can be suitable.
In the above units, the shutter and diaphragm blades may be arranged within a common blade room. Accordingly, the unit can be thin, and the interlocking mechanism between the shutter and diaphragm blades can be simplified.